The extent of the Qualified Watershed Protection Plan for the proposed Katerra project off of State Highway 80 was revealed at the Planning and Zoning Commission’s meeting Tuesday night. The commission approved the plan unanimously.
The plan was the subject of a public hearing and then a vote by the P&Z commissioners. Greg Schwarz, project engineer with the city, gave the staff presentation about the plan, which is required under city rules.
The plan includes a stormwater detention pond on premises plus a batch detention area that collects stormwater runoff from the site’s impervious cover, holds it for 12 hours and releases it over a period of 48 hours.
“It is an approved method by TCEQ (Texas Commission on Environmental Quality) for water quality treatment,” Schwarz said.
The plan also includes a concrete channel to drain water away from the site. The channel ends at State Highway 80. Schwarz said the channel will start out as a 2- to 5-foot-wide concrete channel and open up to a width of 30 feet at the bottom. Schwarz noted that the channel goes through a floodplain. He said engineers looked at modeling of the channel through the floodplain and models showed no rise in water levels.
Schwarz said the Watershed Protection Plan meets the city’s criteria for approval: It meets environmental regulations and mitigates adverse effects on water quality, and it meets the requirements of the Flood Damage Prevention Ordinance, which prohibits causing a rise in water levels.
Mary Beth Harper, who lives near the project site, spoke during the public hearing and voiced concerns about the project.
“That runoff does affect the San Marcos River,” she noted.
Moreover, none of the maps shown Tuesday night included the proposed Blanco River flood mitigation channel or Farm to Market Road 110, which is slated to run adjacent to the development, she said. Harper was also concerned about harm to people downstream.
Dianne Wassenich of the San Marcos River Foundation said she was not speaking in opposition to the project or the plan, but that she had some questions.
“One of the things I couldn’t understand from the presentation is the top channel … was going to be concrete,” she said. “But then there was a larger channel … and I understand it might have had a concrete bottom but perhaps the sides or earthen? I would like to know more about that because it seems that would help it absorb water.”
Wassenich also asked what would happen if more rain fell than the 1.25-inch rain the detention pond is designed to hold.
“But say we have a 3- or 4-inch rain. I would like for somebody to explain to me what happens then,” she said. “I know there are reasons for those kind of numbers about so many inches of rain, and when it floods more than that, are they saying the original capacity of the creek is going to be taken care of?”
Commissioner Mark Gleason said that he had questions about the channel as well. However, he said, “I’m hopeful that what the engineers have done here is actually going to be helpful.”
Commissioner Mike Dillon asked where the channel empties; Schwarz said it would go into a culvert under SH 80 and on to the San Marcos River. Schwarz also said that the channel must contain 100-year rain waters all the way to where the channel combines with the 100-year floodplain.
“Basically this project is containing all that flow within the channel but also within a drainage easement,” he said.
Schwarz also emphasized that the flow coming off the building site must not exceed what it is before development.
“We do want to basically contain it so it doesn’t flood downstream,” he said.
In response to an email the Daily Record sent to the city, Schwarz said after the water reaches the culvert beneath SH 80, the flow will “continue along the natural creek between Hwy. 80 and the San Marcos River.”
Schwarz said this route is consistent with existing flow patterns off the property.
“The proposed Katerra site also includes a stormwater detention system which limits post development flow rates for the 2, 10, 25, and 100-year storms to less than or equal to what exists under predevelopment conditions,” he said.
Chris Chaffee, engineer for Pape Dawson, described the channel as concrete lined at the northern end of the site that transitions to a wider trapezoidal channel with earthen side slopes and eventually becomes 30 feet wide with earthen side slopes.
Dillon asked if there were any representatives from the city of Martindale present.
“Do they have any thoughts on this?” he asked. No one present responded.
Planning chief Shannon Mattingly noted that a small part of the planned Katerra parking lot is in an area that San Marcos did not annex because it lies within the Martindale extraterritorial jurisdiction (ETJ).
“We still are working with the city of Martindale,” she said, adding that any time a property is shared by two ETJs, the authority over water quality and other regulations goes to the larger city.
P&Z Chair Jim Garber steered the discussion back to whether the Watershed Protection Plan meets the criteria required for approval.
“All of these [issues] are very important,” he said, “but as I see it, not relevant to our decision.”
Commissioner Maxfield Baker asked a final question about water quality during the construction phase and what would be required.
“They need to construct it in a phasing manner,” Schwarz said, “... and of course they need to keep all their sediment onsite.”
Builders will have to put up silt fences, sedimentation basins and other measures on site, and city staff will have to approve of the measures taken to keep sediment from running offsite.
In related business, the commission approved the final plat for the Katerra site. The plat calls for the creation of two streets: Van Lee Boulevard and Innovation Boulevard. Planner Tory Carpenter said that normally, final plats fall under consent agenda items for P&Z, but the Watershed Protection Plan had to be approved before the plat could be considered.
